The court heard protesters gathered at the event, also known as the Cardiff Arms Fair, throughout the day.

Murphy made the first call to South Wales Police just before 10.45am from a phone box on Churchill Way, in which she could be heard crying and saying: “I think there’s a bomb in the Motorpoint Arena.”

The second call was made to Media Wales just after 11.20am from a phone box outside McDonald’s on Queen Street, when she said: “I am from Radical Action Against War. We have planted a bomb at the Motorpoint.”

The venue was searched for suspicious packages and nothing was found.

Murphy was arrested at 2.30pm and interviewed at Cardiff Bay Police Station where she told officers: “I think you have arrested the wrong person. I think the people you should have arrested are the arms dealers.”

Cardiff Bay Police Station

Murphy, 63, from Rhondda Street in Swansea , accepted making the phone calls, but denied the two charges against her.

In her defence, Murphy - who chose to represent herself during the trial - told the jury: “I believe with all my heart and mind that war crimes occurred inside the Motorpoint Arena that day.”

Murphy, who has three children, six grandchildren and one great-grandchild, said she had campaigned against war and arms trade for many years.

Summing up, Judge Rees said: “She is entitled to have views about the sale of arms and she was entitled to engage in a peaceful and lawful demonstration.

“However, the strength of her commitment to opposing the arms trade does not entitle her to break the law.”

The public gallery was full for the hearing, with around 30 people attending.

Prosecutors said there were no sentencing guidelines for the offence.

Murphy had two previous convictions for criminal damage, both relating to protests.

Owen Greenhall, defending, said there was a “conscientious motivation”. He said she previously had a job rehabilitating offenders, but resigned before the case as she did not want it to reflect badly upon her employer.

Motorpoint Arena Cardiff (Image: Media Wales)

The judge noted Murphy was an “intelligent, educated and thoughtful” woman.

Judge Rees said: “During the trial, you spoke eloquently about your deeply held opposition to the arms trade, however that does not justify your actions.”

The judge said Murphy’s hoax calls would have diverted the emergency services from protecting the public.

Judge Rees said the police quickly came to the conclusion it was a hoax call, adding: “At the end of the day, no real harm came of this.”

But she said the sight of a building being evacuated could have caused “panic and alarm”.

Murphy was given a 12-week prison sentence, suspended for 18 months, and ordered to pay £2,000 in costs plus a £115 victim surcharge.

Murphy told the judge: “I don’t want to pay.”

The judge replied it was a court order that must be enforced and she could be sent to prison if she did not comply.

Millie Davies, from the Crown Prosecution Service, said: “Deidre Murphy demonstrated a disregard for public safety by making those false claims.

“The emergency services have to be called away from genuine situations when false calls are made, which puts lives at risk and is a drain on public money and resources.

“Murphy denied the offences but the clear evidence put forward by the CPS saw her convicted by the jury.”